Delft University of Technology Wind turbine rotor aerodynamics The IEA MEXICO rotor explained

188 Pages·2017·32.97 MB·English

Delft University of Technology

Wind turbine rotor aerodynamics
The IEA MEXICO rotor explained
Zhang, Ye
DOI
10.4233/uuid:f8112b0f-d697-4e5c-bbff-ea7eae5ab50c
Publication date
2017
Document Version
Final published version
Citation (APA)
Zhang, Y. (2017). Wind turbine rotor aerodynamics: The IEA MEXICO rotor explained.
https://doi.org/10.4233/uuid:f8112b0f-d697-4e5c-bbff-ea7eae5ab50c
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WIND TURBINE ROTOR AERODYNAMICS
THE IEA MEXICO ROTOR EXPLAINED
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WIND TURBINE ROTOR AERODYNAMICS
THE IEA MEXICO ROTOR EXPLAINED
Proefschrift
terverkrijgingvandegraadvandoctor
aandeTechnischeUniversiteitDelft,
opgezagvandeRectorMagnificusprof.ir.K.C.A.M.Luyben,
voorzittervanhetCollegevoorPromoties,
inhetopenbaarteverdedigenopwoensdag14juni2017om12:30uur
door
YE ZHANG
MasterofScienceinThermalEnergyandPowerEngineering
DalianUniversityofTechnology,Dalian,China
geborenteHeilongjiang,China.
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Thisdissertationhasbeenapprovedby:
promotor:Prof.dr.ir.G.J.W.van Bussel
copromotor:Dr.ir.A.H.vanZuijlen
Compositionofthedoctoralcommittee:
RectorMagnificus, voorzitter
Prof.dr.ir.G.J.W.van Bussel TechnischeUniversiteitDelft,promotor
Dr.ir.A.H.vanZuijlen TechnischeUniversiteitDelft,copromotor
Independentmembers:
Prof.dr.ir.G.Eitelberg TechnischeUniversiteitDelft
Prof.dr.N.N.Sørensen TechnicalUniversityofDenmark
Prof.dr.A.P.Schaffarczyk KieUniversity,Germany
Dr.ir.J.G. Schepers EnergyresearchCentreoftheNetherlands
Othermembers:
Prof.dr.ir.drs H.Bijl TechnischeUniversiteitDelft&Leiden
Reservedmembers:
Prof.dr.ir.G.A.M.vanKuik TechnischeUniversiteitDelft
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v
Keywords: MEXICOrotor,rotoraerodynamics,CFD,OpenFOAM,ZigZageffects,
loads overprediction, transition modeling, turbulence modeling, de-
tachededdysimulation,PIV
Printedby: ProefschriftMaken
Cover: Photo is taken from https://www.evwind.es/2015/07/04/offshore-
wind-power-630-mw-london-array-wind-farm-with-175-wind-
turbines/53165
Copyright©2017byYeZhang
ISBN978-94-6186-815-2
Anelectronicversionofthisdissertationisavailableat
http://repository.tudelft.nl/.
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Tomyfamily,fortheirpatience,supportandlove
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C
ONTENTS
Summary ix
Samenvatting xi
1 Introduction 13
1.1 Researchbackground. . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
1.2 Motivationandobjectives. . . . . . . . . . . . . . . . . . . . . . . . . . 19
1.3 Thesisoutline. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
2 Windturbineaerodynamics 23
2.1 2Dairfoilaerodynamics. . . . . . . . . . . . . . . . . . . . . . . . . . . 24
2.2 3Dfinitewingaerodynamics . . . . . . . . . . . . . . . . . . . . . . . . 26
2.3 Windturbinebladeaerodynamics . . . . . . . . . . . . . . . . . . . . . 29
2.4 Rotoraerodynamicsmodeling . . . . . . . . . . . . . . . . . . . . . . . 30
2.4.1 Bladeelementmomentummethod . . . . . . . . . . . . . . . . . 30
2.4.2 Vortexwakemodel. . . . . . . . . . . . . . . . . . . . . . . . . . 35
2.4.3 Navier-Stokesbasedmethod. . . . . . . . . . . . . . . . . . . . . 37
2.5 Conclusions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
3 VerificationandvalidationofOpenFOAMcode 43
3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
3.2 Validationofturbulencemodels . . . . . . . . . . . . . . . . . . . . . . 44
3.2.1 Eddyviscosityturbulencemodel. . . . . . . . . . . . . . . . . . . 44
3.2.2 HybridRANS/LESmodel. . . . . . . . . . . . . . . . . . . . . . . 51
3.3 Validationoftransitionmodels . . . . . . . . . . . . . . . . . . . . . . . 58
3.3.1 Thestructureofk−k −ωtransitionmodel . . . . . . . . . . . . . 58
L
3.3.2 k−k −ωimplementationandcorrectionsinOpenFOAM. . . . . . 58
L
3.3.3 Testcases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
3.4 Conclusions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
4 Experimentalandnumericalstudyofthenon-rotatingMEXICOblade 69
4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
4.2 Experimentalandnumericalsetup . . . . . . . . . . . . . . . . . . . . . 70
4.2.1 Experimentalapproach . . . . . . . . . . . . . . . . . . . . . . . 70
4.2.2 Numericalapproach. . . . . . . . . . . . . . . . . . . . . . . . . 76
4.3 Resultsandanalysis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
4.3.1 Flowatlowanglesofattack . . . . . . . . . . . . . . . . . . . . . 78
4.3.2 TheeffectsofZigZagtape . . . . . . . . . . . . . . . . . . . . . . 90
4.3.3 Flowathighanglesofattack. . . . . . . . . . . . . . . . . . . . . 98
4.4 Conclusions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
vii
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viii CONTENTS
5 Numericalinvestigationof3DrotatingMEXICOrotor 103
5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104
5.2 Windtunnelmeasurementdatabase . . . . . . . . . . . . . . . . . . . . 104
5.2.1 RotatingmeasurementsoftheMEXICOrotoratDNW. . . . . . . . 104
5.2.2 Non-rotatingmeasurementoftheMEXICObladesatTUDelft. . . . 106
5.2.3 2Dstaticairfoilwindtunnelmeasurement. . . . . . . . . . . . . . 106
5.3 RotationmodelinginOpenFOAM. . . . . . . . . . . . . . . . . . . . . . 106
5.4 Resultsanddiscussion . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
5.4.1 AerodynamicloadscomparisonbetweenexperimentandBEMre-
sults . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
5.4.2 VelocityfieldcomparisonwithPIV. . . . . . . . . . . . . . . . . . 110
5.4.3 Crosssectionalrotationaleffects . . . . . . . . . . . . . . . . . . . 114
5.4.4 RadialflowandCoriolisforce . . . . . . . . . . . . . . . . . . . . 122
5.4.5 Transitionaleffects. . . . . . . . . . . . . . . . . . . . . . . . . . 127
5.4.6 Stallconditionatλ=4.17 . . . . . . . . . . . . . . . . . . . . . . 133
5.5 Conclusions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137
6 AerodynamicsstudyoftheTUDelftBlade2rotor 139
6.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140
6.2 ExperimentalandnumericaldescriptionofTUDelftBlade2rotor . . . . . 140
6.3 Resultsandanalysis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143
6.3.1 Velocitydecomposition . . . . . . . . . . . . . . . . . . . . . . . 143
6.3.2 Forceestimationanddecomposition . . . . . . . . . . . . . . . . 148
6.4 Conclusions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151
7 Conclusionsandrecommendations 155
7.1 Conclusions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156
7.1.1 OpenFOAMperformance . . . . . . . . . . . . . . . . . . . . . . 156
7.1.2 Causesofdeviation . . . . . . . . . . . . . . . . . . . . . . . . . 157
7.1.3 Advancednumericalmodeling. . . . . . . . . . . . . . . . . . . . 158
7.2 Recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159
7.2.1 3Dfluidstructureinteraction . . . . . . . . . . . . . . . . . . . . 159
7.2.2 Flowcontrolmodelingonwindturbineblade . . . . . . . . . . . . 159
ACKNOWLEDGEMENTS 169
ListofPublications 171
CurriculumVitæ 173
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S
UMMARY
Windturbinesareoperatingunderverycomplexanduncontrolledenvironmentalcon-
ditions, includingatmosphericturbulence, atmosphericboundarylayereffects, direc-
tional and spatial variations in wind shear, etc. Over the past decades, the size of a
commercialwindturbinehasincreasedconsiderably.Allthecomplexanduncontrolled
conditionsmentionedaboveresultinuncertaintiesofaerodynamicloadscalculationon
verylargewindturbinebladesandthusbetternumericalcodesareneededforpredicting
theloadsinthedesignphase. Withtheaimtoeliminatetheseuncontrolledeffectsand
improvetheaerodynamicmodels,inlastdecades,severalimportantexperimentalcam-
paignsofdifferentwindturbinemodelshavebeenperformedinlargewindtunnels.The
objectiveofsuchexperiments(e.g.usingtheNRELwindturbineandtheMEXICOrotor)
istoprovidehighqualitymeasurementdatawhichcanbeusedtovalidatenumerical
modelsandimprovedifferentfidelitynumericalcodes,particularlyforpredictingwind
turbineaerodynamicloads.
Problems arose as a result of blind comparisons between (initially not disclosed)
measureddataandnumericalpredictions,inwhichlargedeviationswereobservedin
bothcomparisoncampaigns, evenattheeasy-to-predictconditions. Forinstance, all
numerical models, including high fidelity CFD codes, show a poor prediction of sec-
tionalnormalforcefortheMEXICOrotoratdesigntipspeedratio,especiallyasignifi-
cantoverpredictionatthetipregion(r/R=0.82,0.92).Thesediscrepanciesareobserved
andpresentedinmanyresearchreportsandpublicationswithoutaclearunderstanding
ofthecauses.
Therefore,inthisthesis,adetailedandthoroughinvestigationofwindturbinerotor
aerodynamicsisperformedwithbothexperimentalandnumericalapproaches. Firstly,
theopensourceCFDcode(OpenFOAM-2.1.1)isimprovedandvalidatedtoobtainbetter
windturbineaerodynamicsloadsprediction. Beforeapplyingtheopensourcecodefor
investigatingcomplex3Dflow,anOpenFOAMcodehasbeenextensivelyvalidatedand
evaluatedforseveraltwo-dimensionalflowcases,whichispresentedinChapter3. The
numericalresultsoftheOpenFOAMcodecomparewellwithanotheralreadyvalidate
code,theoreticalsolutionorexperimentaldata. Themostpopularlineareddyviscos-
ityturbulencemodels(Spalart-Allmarasandk−ωSST),implementedinOpenFOAM,
havebeenvalidated. Moreover,animplementationerrorofrecentlydevelopedtransi-
tionmodelk−k −ωinOpenFOAMhasbeencorrectedandthecodehasbeenfurther
L
improvedtopredictlaminar-turbulentboundarylayertransitiononawindturbineair-
foil. Basedonthenumericalresultsofthesetwo-dimensionalcases,confidenceisob-
tainedforsimulatingmorecomplex3Dflowusingthiscode.
Secondly,thecausesoflargediscrepanciesbetweentheMEXICOmeasurementand
the numerical results are identified in the thesis. This has been accomplished by re-
assessingtheloadspredictioninthefirstMEXICOcampaignandanalyzingthepossible
causesofdiscrepanciessuchas:1)theverycomplicatedgeometryoftheMEXICOrotor
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